If you use the ham band you must Id the signal (An overlay board costs $75.00-1000 And must be rf proofed)
(1) A piece of cardboard, with your call sign handwritten on it, should cost almost nothing. This works fine if you keep your flights under 10 minutes.
(2) Print the station ID on the model's fuselage within camera view. Cost: free.
(3) Print the station ID on the back of the prop. Most CCD cameras will "freeze" the image. Cost: free.
(4) If your system has audio, just speak the call sign into the mic. This works fine if you keep your flights under 10 minutes. Cost: free.
(5) There are other methods too. Those above are cheap and easy.